In 50 to 90% of infected persons, the first symptoms and signs of HIV infection appear as acute HIV syndrome. The period between the risky event and the occurrence of acute HIC syndrome is usually from one to six weeks. Symptoms stated by infected persons may be very different; from mild, cold-like symptoms with swollen lymph glands to medium severe symptoms resembling influenza; inflammation of the meninges may also appear.

Patients usually have fever, they sweat, have muscle pains, swollen lymph glands; they suffer from nausea or diarrhoea, often develop a reddish rash and small wounds on the skin, in the mouth or anus. Most symptoms pass in 2 to 4 weeks, but the fatigue may last for several months.

This may be followed by a period of several years in which an infected person does not have any problems. Yeast infections or certain skin conditions may be more common, while swollen lymph glands may remain from the period of the acute HIV syndrome. However, the immune system of untreated patients deteriorates inexorably, which causes more and more frequent occurrences of numerous infections and conditions, the course of which would be much less complicated in healthy persons, or would not develop at all. Skin conditions deteriorate (rash, ulcers, recurring herpes. yeast infections of the oral cavity, sexual organs etc.), with very frequent warts of the anus and genitals, atypical pneumonias, weight loss, diarrhoeas and cancerous diseases appear (Kaposi sarcoma, lymphomas, anal cancer etc.), as well as nervous system disorders followed by full emaciation, progressive cancerous diseases and AIDS dementia. The consequences of HIV infection can be reflected on all organ systems.

In untreated persons, AIDS usually develops within 10 years after infection with HIV.